Character display apparatus and character display method, control program for controlling the character display method and recording medium recording the control program

ABSTRACT

A character display apparatus is provided, which comprises a display device comprising a plurality of pixels, and a control section for controlling the display device. Each of the plurality of pixels comprises a plurality of sub-pixels arranged in a predetermined direction. A first pixel of the plurality of pixels comprises a plurality of first sub-pixels. At least one pixel neighboring the first pixel comprises a plurality of second sub-pixels. The control section determines an arrangement pattern containing a plurality of elements, in which a value of each of the plurality of elements is determined depending on whether or not a basic portion indicating a skeleton of a character is assigned to a corresponding sub-pixel of the plurality of the first and second sub-pixels. The control section determines a luminance level of the first pixel based on the arrangement pattern.

TECHNICAL FIELD

The present invention relates to a character display apparatus andmethod capable of displaying characters with a high resolution using acolor display device. The present invention also relates to a controlprogram for controlling the character display method and a recordingmedium in which the control program is recorded.

BACKGROUND ART

Some personal computers, word processors, mobile telephones comprise adisplay section capable of displaying color. As a technique fordisplaying characters with a high resolution in such apparatuses, forexample, Japanese Laid-Open Publication No. 2001-100725 discloses acharacter display apparatus.

This character display apparatus is provided with a plurality of pixelson a display surface thereof Each pixel comprises a plurality ofsub-pixels arranged in a predetermined direction, to which respectivecolors (e.g., Red (R), Green (G), and Blue (B)) are assigned. Thestrength of a color element in a sub-pixel is represented by the levelof the color element which has a plurality of steps, e.g., 0 to 7. If acertain level of color element is assigned to a sub-pixel correspondingto the skeleton of a character, color element levels which vary stepwisearound the sub-pixel are assigned to surrounding sub-pixels. The colorelement levels are arranged in a predetermined pattern. Each colorelement level is converted to a luminance level in accordance withpredetermined correspondence.

The level of a color element corresponds to the degree of the colorelement which contributes to the color of a character. The greater thecontribution of a sub-pixel to the color of a character, the greater thecolor element level of the sub-pixel. The greater the contribution of asub-pixel to the color of a background, the lower the color elementlevel of the sub-pixel. The luminance level of a sub-pixel correspondsto the degree of light emission of the sub-pixel. The greater theluminance level of a sub-pixel, the greater the degree of light emissionof the sub-pixel. The lower the luminance level, the lower the degree oflight emission. Thus, by controlling the color element level on asub-pixel-by-sub-pixel basis so as to display the shapes of characters,the characters can be displayed with a higher resolution than when theluminance level is controlled on a pixel-by-pixel basis. Further, byforming a pattern of color element levels which vary stepwise around asub-pixel corresponding to the skeleton of a character, color noise canbe suppressed.

Japanese Laid-Open Publication No. 2001-184051 discloses anothercharacter display apparatus capable of displaying characters with a highresolution. In this character display apparatus, a predeterminedcorrespondence between the above-described color element level andluminance level is appropriately changed according to the color of acharacter to be displayed and the color of a background. As a result,characters can be displayed with a high resolution in any charactercolor and any background color.

FIG. 12 is a block diagram showing a representative configuration of acharacter display apparatus 1 a as disclosed in Japanese Laid-OpenPublication Nos. 2001-100725 and 2001-184051 described above.

Examples of the character display apparatus 1 a include any informationdisplay apparatuses comprising a display device capable of displayingcolor, such as electronic apparatuses, information apparatuses, and thelike, specifically personal computers and word processors of any type,such as desktop, laptop, and the like. Examples of the character displayapparatus 1 a also include electronic apparatuses comprising a colorliquid crystal display device, such as communication apparatuses (e.g.,personal digital assistants, mobile telephones including PHS, generalfixed telephones, FAX, etc.).

The character display apparatus 1 a comprises a display device 3. Thedisplay device 3 is capable of displaying color. Examples of the displaydevice 3 include liquid crystal displays, organic EL displays, and thelike.

The display device 3 is connected to a control section 20. The controlsection 20 comprises a CPU 2 and a main memory 4. The control section 20separately controls a plurality of color elements corresponding to aplurality of sub-pixels included in the display device 3. The controlsection 20 is connected to an input device 7 and an auxiliary memoryapparatus 40.

The input device 7 is an apparatus for inputting characters to bedisplayed on the display device 3, instructions of the user, and thelike. Examples of the input device 7 include keyboards, touch panels,mice, and the like.

The auxiliary memory apparatus 40 stores a display program 41 a fordisplaying characters, and data 5 including character shape data 5 b, acorrection table 5 c and a luminance table 5 d. Examples of thecharacter shape data 5 b include outline data representing the contourshapes of characters, skeleton data representing the skeletal shapes ofcharacters, bitmap data representing characters, and the like. Note thatprocessing by the display program 41 a slightly varies depending on thetype of the character shape data 5 b. Characters to be displayed mayinclude simple graphics, such as pictographic characters and the like.In the descriptions below, characters are illustrated.

The correction table 5 c is used to determine the color element levelsof sub-pixels neighboring a sub-pixel corresponding to a basic portion.For example, when the color element level of a sub-pixel correspondingto a basic portion is 7, the color element levels of its neighboringsub-pixels are set to be, for example, 5, 2 and 1 from the nearest tothe basic portion. The luminance table 5 d defines a correspondencebetween color element levels and luminance levels.

FIGS. 13A and 13B are diagrams for explaining a display surface of thedisplay device 3. The display surface of the display device 3 isprovided with a plurality of pixels 10 for displaying characters,graphics, and the like as shown in FIG. 13A. Each pixel 10 comprises 3sub-pixels 11 arranged in a predetermined direction (a horizontaldirection in FIG. 13A), to which respective color elements (e.g., Red(R), Green (G), and Blue (B)) are assigned.

When a character is displayed on the display surface, the basic portionrepresenting the skeleton of the character is assigned to sub-pixels 11in pixels 10 associated with the character according to the charactershape data 5 b. For example, when a Kanji character “

” is displayed, the basic portion corresponding to the skeleton of thecharacter is assigned to sub-pixels 11 indicated by hatched portionsshown in FIG. 9.

A process for associating the basic portion representing the skeleton ofa character with sub-pixels 11 varies depending on the type of thecharacter shape data 5 b. For example, outline data contains a charactercode for identifying the type of a character, the number of strokesconstituting a single character (the stroke count of a character), thenumber of contour points constituting a single stroke, the coordinatesof contour points constituting a single stroke, and the like. In thiscase, each stroke has a shape enclosed by a contour line approximated bycurved lines, straight lines, arcs, a combination thereof, or the like,and a predetermined thickness so as to display the contour shape of acharacter. A contour line representing the contour shape of a charactercan be approximated by straight lines, curved lines, arcs, a combinationthereof, or the like, using the coordinate data of contour points. If anarea where the inside of a contour line overlaps a sub-pixel is greaterthan or equal to a predetermined area, such a sub-pixel is determined tocorrespond to a basic portion representing the skeleton of a character.

Skeleton data contains a character code for identifying the type of acharacter, the number of strokes constituting a single character, thenumber of points constituting a single stroke, the line type of a stroke(curved line, straight line, or the like), the coordinates of pointsconstituting a single stroke, and the like. In this case, each stroke isin the form of a line of a certain line type for representing theskeletal shape of a character, and does not have a thickness. If theline type of a stroke is a straight line, the stroke can be approximatedby a straight line passing through a plurality of points constitutingthe stroke using the coordinate data. If the line type of a stroke is acurved line, the stroke can be approximated by a curved line passingthrough a plurality of points constituting the stroke using thecoordinate data. Sub-pixels 11 on a stroke are determined as sub-pixels12 (FIG. 13) corresponding to the basic portion representing theskeleton of a character.

When a sub-pixel 12 corresponding to the basic portion representing theskeleton of a character is determined, the color element levels of thesub-pixel 12 and a sub-pixel 13 neighboring the sub-pixel 12 aredetermined. For example, when a sub-pixel 12 (hatched in FIG. 13B),which is located at the middle of three sub-pixels 11 (FIG. 1 3A)constituting a pixel 10, is determined to correspond to a basic portion,the color element level of the sub-pixel 12 corresponding to the basicportion is set to be “7” which is the maximum level. The color elementlevels of sub-pixels 13 which neighbor the sub-pixel 12 corresponding tothe basic portion and are determined not to correspond to the basicportion, are set according to the correction table 5C whose example isshown in FIG. 10. For example, when a correction pattern 1 is selected,the color element levels of the sub-pixels 13 which neighbor thesub-pixel 12 corresponding to the basic portion, are set to be stepwisedecreased, e.g., “5”, “2”, and “1” with an increase in the distance fromthe sub-pixel 12 corresponding to the basic portion. Alternatively, whena correction pattern 2 is selected, the color element levels of thesub-pixels 13 which neighbor the sub-pixel 12 corresponding to the basicportion, are set to be stepwise decreased, e.g., “4”, “2”, and “1” withan increase in the distance from the sub-pixel 12 corresponding to thebasic portion. The color element level of sub-pixels 14, which arelocated at a distance of four pixels from the sub-pixel 12 correspondingto the basic portion, is set to be “0” which is intended to represent abackground.

Note that when a sub-pixel 13, which does not correspond to a basicportion, neighbors a plurality of sub-pixels 12 corresponding to a basicportion, the color element level of the sub-pixel 13 can take aplurality of values depending on the distance from the sub-pixels 12. Inthis case, the color element level of the sub-pixel 13 is set to be thegreatest value.

The color element level of each sub-pixel is converted to a luminancelevel according to a correspondence between color element levels andluminance levels defined in the luminance table 5 d whose example isshown in FIG. 11. In FIG. 13B, the luminance level of the sub-pixel 12corresponding to the basic portion is set to be “0”. The luminance levelof a sub-pixel having a color element level of “5”, which neighbors thesub-pixel 12, is set to be “73”. The luminance level of a sub-pixelhaving a color element level of “2” is set to be “182”. The luminancelevel of a sub-pixel having a color element level of “1” is set to be“219”. The luminance level of the sub-pixel 14, whose color elementlevel is set to “0” as a background, is set to be “255”.

FIG. 14 is a flowchart indicating a process flow of the display program41 a (FIG. 12) when the character shape data 5 b is skeleton data.

In step S1, a character code and a character size are input through theinput device 7. For example, when a Kanji character “

” is displayed on the display device 3, 4458 (JIS KUTEN code, 44thsection and 58th point) is input as a character code. The character sizeis represented by the number of dots in a horizontal direction and thenumber of dots in a vertical direction, e.g., 20 dots×20 dots, forexample.

In step S2, skeleton data corresponding to the input character code isread from the character shape data 5 b in the auxiliary memory apparatus40 and is then stored in the main memory 4 of the control apparatus 20.This skeleton data contains a character code for identifying the type ofa character, the number of strokes constituting a single character, thenumber of points constituting a single stroke, the line type of astroke, the coordinates of points constituting a single stroke, and thelike.

In step S3, the coordinate data of points constituting each stroke isscaled according to the character size input through the input device 7.This scaling converts the coordinate data in the skeleton data definedin a predetermined coordinate system to a real pixel coordinate systemfor the display device 3. In this case, the scaling is performed byconsidering the arrangement of sub-pixels. As shown in FIG. 13A, forexample, one pixel 10 comprises three sub-pixels 11 arranged in an Xdirection. When a character size is 20 dots×20 dots, the coordinate dataof the skeleton data is scaled into data of 60(=20×3) pixels×20 pixels.

In step S4, the coordinate data of points constituting a stroke isobtained. In step S5, it is determined whether the type of stroke is astraight line or a curved line from the line type of the strokecontained in the skeleton data. When the type of stroke is a straightline, the process goes to step S6. When the type of stroke is a curvedline, but not a straight line, the process goes to step S7.

In step S6, the points constituting the stroke are linked with straightlines, and sub-pixels on the straight lines are defined as the basicportion representing the skeleton of a character. In step S7, thecoordinate data of the points constituting the stroke is approximated bycurved lines, and sub-pixels positioned on the curved lines are definedas the basic portion representing the skeleton of a character.

In step S8, the color element level of the sub-pixel corresponding tothe basic portion representing the skeleton of the character, which isdefined in step S6 or step S7, is set to be “7” which is the maximumcolor element level. Next, in step S9, the color element levels ofsub-pixels neighboring the sub-pixel corresponding to the basic portionare set according to the correction table 5 c.

In step S10, it is determined whether or not all strokes contained in acharacter have been processed. If “Yes”, the process goes to step S11.If “No”, the process returns to step S3 and is continued. In step S11,the color element levels of the sub-pixels are converted to respectiveluminance levels according to the luminance table 5 d indicating thecorrespondence between color element levels and luminance levels. Instep S12, luminance data indicating the luminance levels of thesub-pixels determined in step S11 is transferred to the display device3.

In this manner, luminance levels are adjusted on asub-pixel-by-sub-pixel basis to display a character on the displaydevice 3. In this case, sub-pixels corresponding to the basic portionrepresenting the skeleton of a character are obtained from the skeletondata. Alternatively, such sub-pixels may be obtained from outline data,bitmap data, or the like by a predetermined process. Alternatively, thepattern of the basic portion may be previously stored as character shapedata in the auxiliary memory apparatus 40 and may be read as required.

In the above-described conventional technique, a pattern of the colorelement levels of sub-pixels constituting a character is determined, andthereafter, the color element levels are converted to respectiveluminance levels which are actually displayed on a display section.Therefore, the process is complicated and a working memory area requiredfor the process is increased. As a result, character display processingis slowed, the hardware cost is increased, and the like.

In the above-described conventional technique, when two or more strokeshaving a predetermined width are near to or cross each other, the spaceportion within a character is reduced so that the shape of the characteris hardly recognized, i.e., “deformed character”. To avoid this, apattern of the color element levels of sub-pixels is changed. However,it is a complicated task to change a pattern of color element levels byactually recognizing the positional relationship between strokes.

When colors can be arbitrarily assigned to characters and backgrounds tobe displayed, some combination of the color of a character and the colorof a background may not be suitable for a pattern of color elementlevels, resulting in a degradation in the shape of a character and asignificant reduction in the visibility of the character.

DISCLOSURE OF THE INVENTION

According to one aspect of the present invention, a character displayapparatus comprises a display device comprising a plurality of pixels,and a control section for controlling the display device. Each of theplurality of pixels comprises a plurality of sub-pixels arranged in apredetermined direction, and at least one of a plurality of colorelements is assigned to each of the plurality of sub-pixel. The controlsection determines at least one sub-pixel, to which a basic portionindicating a skeleton of a character is assigned, among the plurality ofsub-pixels in the display device, based on character shape dataindicating character shapes. A first pixel of the plurality of pixelscomprises a plurality of first sub-pixels. At least one pixelneighboring the first pixel comprises a plurality of second sub-pixels.The control section determines an arrangement pattern containing aplurality of elements, in which a value of each of the plurality ofelements is determined depending on whether or not the basic portion isassigned to a corresponding sub-pixel of the plurality of the firstsub-pixels and the plurality of the second sub-pixels. The controlsection determines a luminance level of the first pixel based on thearrangement pattern.

In one embodiment of this present invention, the plurality of elementsinclude a first element and a second element neighboring the firstelement. A value of the first element indicates that the basic portionis assigned to a sub-pixel relating to the first element. A value of thesecond element indicates that the basic portion is not assigned to asub-pixel relating to the second element. The control section determinesthe luminance level of the first pixel based on another arrangementpattern which is modified from said arrangement pattern such that avalue of the first element is interchanged with a value of the secondelement.

In one embodiment of this invention, the plurality of elements include afirst element and a second element neighboring the first element. Avalue of the first element indicates that the basic portion is assignedto a sub-pixel relating to the first element. A value of the secondelement indicates that the basic portion is not assigned to a sub-pixelrelating to the second element. The control section determines theluminance level of the first pixel based on another arrangement patternwhich is modified from said arrangement pattern such that a value of thesecond element is changed to indicate that the basic pattern is assignedto the sub-pixel relating to the second element.

In one embodiment of this invention, the control section determines theluminance level of the first pixel based on a combination of a color ofthe character and a background color of the character and thearrangement pattern.

In one embodiment of this invention, the control section compares acombination of a color of the character and a background color of thecharacter with a combination of a predetermined character color and apredetermined background color, and determines the luminance level ofthe first pixel based on a result of the comparison and the arrangementpattern.

According to another aspect of the present invention, a method fordisplaying a character on a character display apparatus is provided. Thecharacter display apparatus comprises a display device comprising aplurality of pixels and a control section for controlling the displaydevice. Each of the plurality of pixels comprises a plurality ofsub-pixels arranged in a predetermined direction, and at least one of aplurality of color elements is assigned to each of the plurality ofsub-pixel. A first pixel of the plurality of pixels comprises aplurality of first sub-pixels. At least one pixel neighboring the firstpixel comprises a plurality of second sub-pixels. The method comprisesthe steps of determining at least one sub-pixel, to which a basicportion indicating a skeleton of a character is assigned, among theplurality of sub-pixels in the display device, based on character shapedata indicating character shapes, determining an arrangement patterncontaining a plurality of elements, in which a value of each of theplurality of elements is determined depending on whether or not thebasic portion is assigned to a corresponding sub-pixel of the pluralityof the first sub-pixels and the plurality of the second sub-pixels, anddetermining a luminance level of the first pixel based on thearrangement pattern.

According to another aspect of the present invention, a program forcausing a character display apparatus to execute a character displayprocess is provided. The character display apparatus comprises a displaydevice comprising a plurality of pixels and a control section forcontrolling the display device. Each of the plurality of pixelscomprises a plurality of sub-pixels arranged in a predetermineddirection, and at least one of a plurality of color elements is assignedto each of the plurality of sub-pixel. A first pixel of the plurality ofpixels comprises a plurality of first sub-pixels. At least one pixelneighboring the first pixel comprises a plurality of second sub-pixels.The character display process comprises the steps of determining atleast one sub-pixel, to which a basic portion indicating a skeleton of acharacter is assigned, among the plurality of sub-pixels in the displaydevice, based on character shape data indicating character shapes,determining an arrangement pattern containing a plurality of elements,in which a value of each of the plurality of elements is determineddepending on whether or not the basic portion is assigned to acorresponding sub-pixel of the plurality of the first sub-pixels and theplurality of the second sub-pixels, and determining a luminance level ofthe first pixel based on the arrangement pattern.

According to another aspect of the present invention, a recording mediumstoring a program for causing a character display apparatus to execute acharacter display process is provided. The recording medium is readableby the character display apparatus. The character display apparatuscomprises a display device comprising a plurality of pixels and acontrol section for controlling the display device. Each of theplurality of pixels comprises a plurality of sub-pixels arranged in apredetermined direction, and at least one of a plurality of colorelements is assigned to each of the plurality of sub-pixel. A firstpixel of the plurality of pixels comprises a plurality of firstsub-pixels. At least one pixel neighboring the first pixel comprises aplurality of second sub-pixels. The character display process comprisesthe steps of determining at least one sub-pixel, to which a basicportion indicating a skeleton of a character is assigned, among theplurality of sub-pixels in the display device, based on character shapedata indicating character shapes, determining an arrangement patterncontaining a plurality of elements, in which a value of each of theplurality of elements is determined depending on whether or not thebasic portion is assigned to a corresponding sub-pixel of the pluralityof the first sub-pixels and the plurality of the second sub-pixels, anddetermining a luminance level of the first pixel based on thearrangement pattern.

Functions of the present invention will be described below.

According to the present invention, the display surface of the displaysection is provided with a plurality of pixels each containing aplurality of sub-pixels arranged in a predetermined direction. At leastone of a plurality of color elements is assigned to each sub-pixel. Whendisplaying a character on the display surface of the display section,sub-pixels corresponding to the basic portion representing the skeletonof a character are determined from the sub-pixels based on charactershape data representing the shapes of characters, such as skeleton datarepresenting the skeletal shapes of characters, outline datarepresenting the contour shapes of characters, bitmap data representingcharacters, or the like. The arrangement pattern of sub-pixels in apixel whose luminance level is to be determined and its neighboringsub-pixels are determined. Based on the arrangement pattern ofsub-pixels, the luminance levels of sub-pixels contained in the pixelare determined. The luminance levels of all pixels in the displaysurface are determined in this manner so that the character is displayedon the display section.

Therefore, when displaying characters with high resolution and highdefinition, luminance levels can be determined only by extractingarrangements of sub-pixels corresponding to a basic portion (as usedherein, the term “arrangement of sub-pixels corresponding to a basicportion” indicates an arrangement of sub-pixels each corresponding to abasic portion or a non-basic portion of a character). Therefore,processes can be simplified and the processes can be performed atpractical speed even using a CPU having a low processing speed, ascompared to a conventional technique in which the color element level ofa sub-pixel corresponding to a basic portion and the color elementlevels of sub-pixels neighboring that sub-pixel are determined beforethe color element levels are used to determine the color luminance levelof a pixel of interest. Further, the size of a control programdescribing a procedure can be reduced, thereby making it possible toreduce the size of an auxiliary memory apparatus. Furthermore, thesimplification of processes can reduce a working memory region requiredduring processing. As a result, the cost of a character displayapparatus can be reduced, thereby making it possible to realize acharacter display with high resolution and high definition.

According to the present invention, when the luminance levels ofsub-pixels contained in a pixel of interest are determined based on thearrangement of sub-pixels corresponding to a basic portion, the positionof a sub-pixel corresponding to a basic portion is replaced with itsneighboring sub-pixel, and the arrangement of sub-pixels including sucha replacement is used to determine the luminance levels of sub-pixelscontained in a pixel of interest. Therefore, when sub-pixelscorresponding to the skeleton of a character are close to each other,the arrangement of sub-pixels can be changed so that such sub-pixels arespaced to a further distance. Thereby, it is possible to prevent spacewithin a character from being diminished to deform the character whenstrokes of the character are close to each other. The arrangement ofsub-pixels corresponding to the skeleton of a character may not besuitable for the shape of the character, depending on a colorcombination of a character and a background. Even in this situation, bychanging the arrangement of sub-pixels corresponding to the skeleton,distortion of the character can be corrected.

According to the present invention, when the luminance levels ofsub-pixels contained in a pixel of interest is determined based on thearrangement of sub-pixels corresponding to a basic portion, a sub-pixelcorresponding to a basic portion is duplicated and provided to itsneighboring sub-pixel. The arrangement of sub-pixels including theduplicate sub-pixels can be used to determine the luminance levels ofsub-pixels contained in a pixel of interest. Thus, a sub-pixelcorresponding to the skeleton of a character can be multiplexed, therebymaking it possible to simplify a process of thickening the line width ofa character so that the process can be efficiently performed.

According to the present invention, when the luminance levels ofsub-pixels contained in a pixel of interest are determined based on thearrangement of sub-pixels corresponding to a basic portion, thecorrespondence between the arrangement of sub-pixels and the luminancelevels of sub-pixels contained in a pixel of interest can be changeddepending on a combination of a character color and a background color.Therefore, the optimum luminance levels of sub-pixels contained in apixel of interest can be determined depending on a character color and abackground color. Therefore, characters having an optimum line width canbe displayed for each color combination, whereby characters can bedisplayed with a high level of visibility irrespective of a colorcombination.

According to the present invention, when the luminance levels ofsub-pixels contained in a pixel of interest are determined based on thearrangement of sub-pixels corresponding to a basic portion, thecorrespondence between the arrangement of sub-pixels and the luminancelevels of sub-pixels contained in a pixel of interest can be changedaccording to the size of the difference between character and backgroundcolors previously registered and character and background colors to bedisplayed. The above-described correspondence can be shared by a groupof characters having similar color combinations (similar luminancelevels of sub-pixels), whereby characters can be displayed with a morevariety of color combinations and an optimum line width whilesuppressing the storage capacity of a character display apparatus to asmall level.

Thus, the invention described herein makes possible the advantages of(1) providing a character display apparatus and method capable ofdisplaying characters with a high resolution and definition by a simpleprocess, wherein the speed of character display processing is increasedand the hardware cost can be decreased; (2) a control program forcontrolling the character display method; and a recording medium inwhich the control program is stored.

These and other advantages of the present invention will become apparentto those skilled in the art upon reading and understanding the followingdetailed description with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a configuration of a character displayapparatus according to an embodiment of the present invention.

FIGS. 2A to 2C are diagrams for explaining an arrangement of sub-pixelsand a correction pattern in a character display apparatus according toan embodiment of the present invention.

FIG. 3 is a diagram showing an example of a pixel value table in acharacter display apparatus according to an embodiment of the presentinvention.

FIG. 4 is a diagram showing another example of a pixel value table in acharacter display apparatus according to an embodiment of the presentinvention.

FIG. 5 is a diagram showing another example of a pixel value table in acharacter display apparatus according to an embodiment of the presentinvention.

FIG. 6 is a diagram showing another example of a pixel value table in acharacter display apparatus according to an embodiment of the presentinvention.

FIG. 7 is a diagram showing another example of a pixel value table in acharacter display apparatus according to an embodiment of the presentinvention.

FIG. 8 is a flowchart for explaining a character display methodaccording to an embodiment of the present invention.

FIG. 9 is a diagram showing an exemplary pattern of sub-pixelscorresponding to a basic portion for a Kanji character “

”.

FIG. 10 is a diagram showing an exemplary correction table in acharacter display apparatus.

FIG. 11 is a diagram showing an exemplary luminance table in a characterdisplay apparatus.

FIG. 12 is a block diagram showing a structure of a conventionalcharacter display apparatus.

FIGS. 13A and 13B are diagrams for explaining a structure of sub-pixelsand a correction pattern in a conventional character display apparatus.

FIG. 14 is a flowchart for explaining a conventional character displaymethod.

FIG. 15 is a diagram showing a portion of bitmap data representinggraphics.

FIG. 16 is a diagram showing a portion of a display surface of a displaydevice.

FIG. 17A is a diagram showing a bit of interest and 8 neighbors inbitmap data.

FIG. 17B is a diagram showing a sub-pixel associated with a basicportion according to a basic portion definition rule in the bit ofinterest and its 8 neighbors of FIG. 17A.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described by way ofillustrative examples with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a configuration of a character displayapparatus according to an embodiment of the present invention. Examplesof the character display apparatus 1 b include any information displayapparatuses comprising a display device capable of displaying color,such as electronic apparatuses, information apparatuses, and the like,specifically personal computers and word processors of any type, such asdesktop, laptop, and the like. Examples of the character displayapparatus 1 b also include electronic apparatuses comprising a colorliquid crystal display device, such as communication apparatuses (e.g.,personal digital assistants, mobile telephones including PHS, generalfixed telephones, FAX, etc.).

The character display apparatus 1 b comprises a display device 3comprising a plurality of pixels. The display device 3 is capable ofdisplaying color. Examples of the display device 3 include liquidcrystal displays, organic EL displays, and the like.

The display device 3 is connected to a control section 20. The controlsection 20 controls the operation of the display device 3. The controlsection 20 comprises a CPU 2 and a main memory 4. The control section 20separately controls a plurality of color elements corresponding to aplurality of sub-pixels included in the display device 3. The controlsection 20 is connected to an input device 7 and an auxiliary memoryapparatus 40.

The input device 7 is an apparatus for inputting characters to bedisplayed on the display device 3, instructions of the user, and thelike. Examples of the input device 7 include keyboards, touch panels,mice, and the like.

The auxiliary memory apparatus 40 stores a display program 41 b fordisplaying characters and data 5 containing character shape data 5 b anda pixel value table 5 e. A recording medium 8 (e.g., an optical disc),which is readable by the character display apparatus 1 b, stores thedisplay program 41 b and the data 5. The display program 41 b and thedata 5 may be installed from the recording medium 8 to the auxiliarymemory apparatus 40 or may be previously stored in the auxiliary memoryapparatus 40. Examples of the character shape data 5 b include outlinedata representing the contour shapes of characters, skeleton datarepresenting the skeletal shapes of characters, bitmap data representingcharacters, and the like. Note that processing by the display program 41b slightly varies depending on the type of the character shape data 5 b.Characters to be displayed may include simple graphics, such aspictographic characters and the like. In descriptions below, charactersare illustrated.

The pixel value table 5 e contains a correspondence between thearrangement pattern of a basic portion comprising M+2×N sub-pixels (Msub-pixels contained in a pixel (pixel of interest) whose luminancelevel is determined and N sub-pixels neighboring each side of the Msub-pixels), and the luminance levels (pixel value) of the M sub-pixelsof the pixel of interest.

FIGS. 2A to 2C are diagrams for explaining a display surface of thedisplay device 3. The display surface of the display device 3 isprovided with a plurality of pixels 10 for displaying characters,graphics, and the like as shown in FIG. 2A. Each pixel 10 comprises 3sub-pixels 11 arranged in a predetermined direction (a horizontaldirection in FIG. 2A), to each of which at least one color element(e.g., Red (R), Green (G), and Blue (B)) is assigned.

When a character is displayed on the display surface, the basic portionrepresenting the skeleton of the character is assigned to sub-pixels 11in pixels 10 associated with the character according to the charactershape data 5 b. For example, when a Kanji character “

” is displayed, the basic portion corresponding to the skeleton of thecharacter is assigned to sub-pixels 11 indicated by hatched portionsshown in FIG. 9.

A process for associating the basic portion representing the skeleton ofa character with sub-pixels 11 varies depending on the type of thecharacter shape data 5 b. For example, outline data contains a charactercode for identifying the type of a character, the number of strokesconstituting a single character (the stroke count of a character), thenumber of contour points constituting a single stroke, the coordinatesof contour points constituting a single stroke, and the like. In thiscase, each stroke has a shape enclosed by a contour line approximated bycurved lines, straight lines, arcs, a combination thereof, or the like,and a predetermined thickness so as to display the contour shape of acharacter. A contour line representing the contour shape of a charactercan be approximated by straight lines, curved lines, arcs, a combinationthereof, or the like, using the coordinate data of contour points. If anarea where the inside of a contour line overlaps a sub-pixel is greaterthan or equal to a predetermined area, such a sub-pixel is determined tocorrespond to a basic portion representing the skeleton of a character.

Skeleton data contains a character code for identifying the type of acharacter, the number of strokes constituting a single character, thenumber of points constituting a single stroke, the line type of a stroke(curved line, straight line, or the like), the coordinates of pointsconstituting a single stroke, and the like. In this case, each stroke isin the form of a line of a certain line type for representing theskeletal shape of a character, and does not have a thickness. If theline type of a stroke is a straight line, the stroke can be approximatedby a straight line passing through a plurality of points constitutingthe stroke using the coordinate data. If the line type of a stroke is acurved line, the stroke can be approximated by a curved line passingthrough a plurality of points constituting the stroke using thecoordinate data. Sub-pixels 11 on a stroke are determined as sub-pixels12 (FIG. 2B) corresponding to the basic portion representing theskeleton of a character.

The bitmap data has binary values. Each bit constituting the bitmap datahas a value of “1” or “0”. A bit having a value of “1” represents ablack portion in graphics. A bit having a value of “0” represents awhite portion in a graphic. A basic portion of a graphic corresponds toa core in a graphic. When a graphic is a character, the basic portion isa middle portion of a stroke. In the bitmap data, stroke information islost. Bits in the bitmap data are associated with the basic portion byinference. The basic portion cannot be inferred only by information ofbit D(x, y) of interest. However, the basic portion is inferred based oninformation of bits neighboring bit D of interest. It is initiallydetermined whether or not each bit constituting the bitmap data is “1”,so as to investigate the “1”/“0” arrangement pattern of neighboring bitsaround the bit of interest. The bit of interest is associated with apixel. Among the subpixels of the pixel with which the bit of interestis associated, a sub-pixel 12 corresponding to the basic portion isdetermined according to the arrangement pattern of the neighboring bits.

FIG. 15 is a diagram showing a portion of bitmap data representing agraphic. D(x, y) represents a bit of interest. N(a, b) represents bitD(x+a, y+b) around D(x, y). FIG. 15 shows eight bits N(−1, 1), N(0, −1),N(1, −1), N(−1, 0), N(1, 0), N(−1, 1), N(0, 1), and N(1, 1) neighboringbit D(x, y) in a vertical, horizontal, or slant direction. These eightneighboring bits are called eight neighbors. N(a, b) and D(x, y) eachhas a value of “1” or “0”.

FIG. 16 is a diagram showing a portion of the display surface of adisplay device. P(x, y) represents a pixel on the display surface. BitD(x, y) shown in FIG. 15 is associated with pixel P(x, y) when a graphicrepresented by bitmap data is displayed on a display device. P(x, y)contains three sub-pixels C(3x, y), C(3x+1, y) and C(3x+2, y). When D(x, y) has a value of “1”, a sub-pixel corresponding to a basic portionis determined among the three sub-pixels C(3x, y), C(3x+1, y) andC(3x+2, y) according to a definition rule. When D(x, y) has a value of“0”, none of the three sub-pixels is determined as a sub-pixelcorresponding to the basic portion. Note that although bit D(x, y) shownin FIG. 15 is associated with a sub-pixel group Grp shown in FIG. 16,the number of sub-pixels contained in a group is not necessarily equalto the number of sub-pixels contained in a pixel. For example, a bit inthe bitmap data may be associated with a group Grp′ consisting of foursub-pixels shown in FIG. 16. The direction of arrangement of sub-pixelsin a group is not limited to an X direction. For example, a bit in thebitmap data may be associated with a group Grp″ in which sub-pixels arearranged in the X direction and the Y direction as shown in FIG. 16.

FIG. 17A shows an example of 8 neighbors of a bit of interest D(x, y) inthe bitmap data. Bit N(a, b) having a value of “1” is represented byN(a, b). In FIG. 17A, N(0, −1)=N(1, 1)=1, N(1, 0)=N(0, 1)=N(−1, 1)=N(−1,0)=0, and N(−1, −1) and N(1, −1) represented by “※” has any one of “0”and “1”. FIG. 17B is a diagram showing a sub-pixel which is associatedwith a basic portion according to a basic portion definition rule when 8neighboring bits of bit D(x, y) have values shown in FIG. 17A. Accordingto the basic portion definition rule, whether or not each of threesub-pixels contained in pixel P(x, y) is associated with a basic portionis determined based on the arrangement of “0” and “1” of bits N(a, b)around bit D(x, y) associated with pixel P(x, y) as follows. Note thatbit D(x, y) is assumed to have a value of “1” below. As shown in FIG.16, pixel P(x, y) on the display surface corresponding to bit D(x, y)contains three sub-pixels C(3x, y), C(3x+1, y) and C(3x+2, y). Amongthese sub-pixels, a sub-pixel having a value of “1” in FIG. 17B isassociated with a basic portion, while sub-pixels having a value of “0”are not associated with a basic portion. Specifically, sub-pixel C(3x+2,y) is associated with a basic portion, while C(3x, y) and C(3x+1, y) arenot associated with a basic portion. For example, in the bitmap data ofFIG. 17A, a stroke is inferred to be a curved line (dashed line 50 inFIG. 17A) which passes through areas corresponding to bits N(0, −1),D(x, y), and N(1, 1). Such a curved line is considered to pass throughthe right-hand side of an area corresponding to bit D(x, y). Therefore,in FIG. 17B, sub-pixel C(3x+2, y) on the right-hand side of pixel P(x,y) corresponding to bit D(x, y) is associated with a basic portion.

When a sub-pixel 12 corresponding to the basic portion representing theskeleton of a character is determined, the color element levels of thesub-pixel 12 and a sub-pixel 13 neighboring the sub-pixel 12 aredetermined. For example, when a sub-pixel 12 (hatched in FIG. 2B), whichis located at the middle of three sub-pixels 11 (FIG. 2A) constituting apixel 10, is determined to correspond to a basic portion, the colorelement level of the sub-pixel 12 corresponding to the basic portion isset to be “7” which is the maximum level. The color element levels ofsub-pixels 13 which neighbor the sub-pixel 12 corresponding to the basicportion and are determined not to correspond to the basic portion, areset to be stepwise decreased, e.g., “5”, “2”, and “1” with an increasein the distance from the sub-pixel 12 corresponding to the basicportion. The color element level of sub-pixels 14, which are located ata distance of four pixels from the sub-pixel 12 corresponding to thebasic portion, is set to be “0” which is intended to represent abackground.

Note that when a sub-pixel 13, which does not correspond to a basicportion, neighbors a plurality of sub-pixels 12 corresponding to a basicportion, the color element level of the sub-pixel 13 can take aplurality of values depending on the distance from the sub-pixels 12. Inthis case, the color element level of the sub-pixel 13 is set to be thegreatest value.

The color element level of each sub-pixel is converted to a luminancelevel according to a correspondence between color element levels andluminance levels. In FIG. 2B, the luminance level of the sub-pixel 12corresponding to the basic portion is set to be “0”. The luminance levelof a sub-pixel having a color element level of “5”, which neighbors thesub-pixel 12, is set to be “73”. The luminance level of a sub-pixelhaving a color element level of “2” is set to be “182”. The luminancelevel of a sub-pixel having a color element level of “1” is set to be“219”. The luminance level of the sub-pixel 14, whose color elementlevel is set to “0” as a background, is set to be “255”.

In this embodiment, a luminance level is determined as follows. As shownin FIG. 2C, a sub-pixel(s) corresponding to a basic portion (i.e., asub-pixel(s) to which a basic portion is assigned) is extracted fromM+2×N sub-pixels (M sub-pixels 16 contained in a pixel (pixel ofinterest) 15 whose luminance level is to be determined and N sub-pixels17 neighboring on each side of pixel 15). Based on the arrangementpattern of the extracted sub-pixel(s), the luminance levels (i.e., pixelvalue) of M sub-pixels 16 contained in the pixel 15 of interest aredetermined.

FIG. 3 is a diagram showing an example of the pixel value table 5 e. InFIG. 3 and FIGS. 4 to 7, it is assumed that the number (M) of thesub-pixels 16 contained in the pixel 15 of interest shown in FIG. 2C is3 (M=3), and the number (N) of the sub-pixels 17 on each side of thepixel 15 is 3 (N=3). Note that the number N of the above-describedpixels is typically the same as the number of elements in a correctionpattern (N=3 in FIG. 10). The left-hand side of FIG. 3 shows anarrangement pattern of 9 sub-pixels contained in 3 pixels (the pixel 15of interest and pixels on the both sides thereof) which are arranged inthe same direction as that of the arrangement of the sub-pixels. Anarrangement pattern contains a plurality of elements. The value of eachelement is determined by the control section 20 depending on whether ornot a basic portion is assigned to a corresponding sub-pixel of thesubpixels 16 and the subpixels 17. In the figures, element “0” indicatesthat a basic portion is not assigned to a sub-pixel relating to theelement; element “1” indicates that a basic portion is assigned to asub-pixel relating to the element; and element “x” indicates that eithera basic portion is assigned to a sub-pixel relating to the element or abasic portion is not assigned to a sub-pixel relating to the element.The right-hand side of FIG. 3 shows the luminance value of eachsub-pixel (R, G, B) contained in a pixel of interest corresponding tothe arrangement pattern on the left side of FIG. 3.

The pixel value of a pixel is determined using the pixel value table 5 eindicating a correspondence between the arrangement pattern ofsub-pixels corresponding to the basic portion of a character and theluminance values of sub-pixels contained in a pixel whose pixel value(the luminance levels of sub-pixels) is to be determined. Theabove-described correspondence indicated by the pixel value table 5 e ispredetermined.

For example, it is assumed that the arrangement pattern of sub-pixelscorresponding to a basic portion is “x10 000 O1x”. For example, when thecorrespondence indicated by the pixel value table 5 e has beendetermined using the correction pattern 1 shown in FIG. 10, thearrangement of the color element levels is “x75, 212, 57x”. The colorelement levels (2, 1, 2) of sub-pixels (R, G, B) contained in a pixel ofinterest whose pixel value is to be determined are converted toluminance levels (182, 219, 182) when the correspondence indicated bythe pixel value table 5 e has been determined using the correspondencebetween color element levels and luminance levels shown in FIG. 11.Therefore, in the pixel value table 5 e of FIG. 3, the arrangementpattern “x1O 000 01x” of the sub-pixels corresponding to a basic portionpreviously corresponds to the pixel values (182, 219, 182) of the pixel.The other arrangement patterns previously correspond to the pixel valuesof pixels.

Note that when a pixel of interest is located at an end of a displaydevice, no neighboring pixel is present at one side of the pixel ofinterest. In this case, another process is performed. For example, whena pixel of interest is located at an end of a display device, theluminance level of the pixel of interest may be inevitably set to (255,255, 255).

FIG. 4 is a diagram showing another example of the pixel value table 5.The left-hand side of FIG. 4 shows an arrangement pattern of 9sub-pixels contained in 3 pixels which are arranged in the samedirection as that of the arrangement of the sub-pixels. The right-handside of FIG. 4 shows the luminance value of each sub-pixel (R, G, B)contained in a pixel of interest corresponding to the arrangementpattern on the left side of FIG. 4.

The pixel value of a pixel is determined using the pixel value table 5 eindicating a correspondence between the arrangement pattern ofsub-pixels corresponding to the basic portion of a character and theluminance values of sub-pixels contained in a pixel whose pixel value isto be determined.

For example, it is assumed that the arrangement pattern of sub-pixelscorresponding to a basic portion is “000 001 000”. For example, when thecorrespondence indicated by the pixel value table 5 e has beendetermined using the correction pattern 1 shown in FIG. 10, thearrangement of the color element levels is “001, 257, 521”. The colorelement levels (2, 5, 7) of sub-pixels (R, G, B) contained in a pixel ofinterest whose pixel value is to be determined are converted toluminance levels (182, 73, 0) when the correspondence indicated by thepixel value table 5 e has been determined using the correspondencebetween color element levels and luminance levels shown in FIG. 11.Therefore, in the pixel value table 5 e of FIG. 4, the arrangementpattern “000 001 000” of the sub-pixels corresponding to a basic portionpreviously corresponds to the pixel values (182, 73, 0) of the pixel.The other arrangement patterns previously correspond to the pixel valuesof pixels.

As described above, the correspondence between the arrangement patternof sub-pixels corresponding to a basic portion and the luminance valuesof the sub-pixels is predetermined in the pixel value table 5 e.Therefore, when sub-pixels corresponding to a basic portion are neareach other, the pixel values of pixels present between strokes can becontrolled by adjusting the luminance values of sub-pixels correspondingto the arrangement pattern. Therefore, it is possible to prevent blackpixels from filling between strokes of a character, i.e., space withinthe character is diminished, or the like. Thus, the quality of displaycan be improved.

FIG. 5 is a diagram showing another example of the pixel value table 5e. In this example, a basic portion is moved in order to prevent spacewithin a character from being diminished. The left-hand side of FIG. 5shows an arrangement pattern of 9 sub-pixels contained in 3 pixels whichare arranged in the same direction as that of the arrangement of thesub-pixels. The middle of FIG. 5 shows an arrangement pattern ofsub-pixels in which the value of an element relating to a sub-pixel tothe left-handed side of the arrangement pattern to which a basic portionis assigned, is replaced with the value “0” of an element relating to asub-pixel located at the middle of three sub-pixels contained in eachpixel (a sub-pixel neighboring the sub-pixel to which a basic portion isassigned). The right-hand side of FIG. 5 shows the luminance value ofeach sub-pixel (R, G, B) contained in a pixel of interest, correspondingto each arrangement pattern in the middle of FIG. 5.

The pixel value of a pixel is determined using the pixel value table 5 eindicating a correspondence between the arrangement pattern ofsub-pixels corresponding to the basic portion of a character and theluminance values of sub-pixels contained in a pixel whose pixel value isto be determined.

For example, it is assumed that the arrangement pattern of sub-pixelscorresponding to a basic portion is “000 001 000”. By replacement of thebasic portion, the arrangement of the sub-pixels is changed to “000 010000”. In this case, when the correspondence indicated by the pixel valuetable 5 e has been determined using the correction pattern 1 shown inFIG. 10, the arrangement of the color element levels is “012, 575, 210”.The color element levels (5, 7, 5) of sub-pixels (R, G, B) contained ina pixel of interest whose pixel value is to be determined are convertedto luminance levels (73, 0, 73) when the correspondence indicated by thepixel value table 5 e has been determined using the correspondencebetween color element levels and luminance levels shown in FIG. 11.Therefore, in the pixel value table 5 e of FIG. 5, the arrangementpattern “000 001 000” of the sub-pixels corresponding to a basic portionpreviously corresponds to the pixel values (73, 0, 73) of the pixel. Theother arrangement patterns previously correspond to the pixel values ofpixels.

FIG. 6 is a diagram showing another example of the pixel value table 5e. In FIG. 6, a duplicate of a basic portion is provided on the leftside of the basic portion to thicken the line width of a character(multiplexing). The left-hand side of FIG. 6 shows an arrangementpattern of 9 sub-pixels contained in 3 pixels which are arranged in thesame direction as that of the arrangement of the sub-pixels. The middleof FIG. 6 shows an arrangement pattern, in which in addition to asub-pixel corresponding to a basic portion, a sub-pixel neighboring tothe left-handed side of that pixel is changed to correspond to a basicportion where the value of a corresponding element of the arrangementpattern is changed “0” to “1”. The right-hand side of FIG. 6 shows theluminance value of each sub-pixel (R, G, B) contained in a pixel ofinterest, corresponding to each arrangement pattern in the middle ofFIG. 6.

The pixel value of a pixel is determined using the pixel value table 5 eindicating a correspondence between the arrangement pattern ofsub-pixels corresponding to the basic portion of a character and theluminance values of sub-pixels contained in a pixel whose pixel value tobe determined.

For example, it is assumed that the arrangement of sub-pixelscorresponding to a basic portion is “x10 000 01x x”. By providing aduplicate of the basic portion to the left-hand side of the sub-pixel,the arrangement of the sub-pixels is changed to “x10 010 11x x”. In thiscase, when the correspondence indicated by the pixel value table 5 e hasbeen determined using the correction pattern 1 shown in FIG. 10, thearrangement of the color element levels is “x75, 225, 77x, x”. The colorelement levels (2, 2, 5) of sub-pixels (R, G, B) contained in a pixel ofinterest whose pixel value is to be determined are converted toluminance levels (182, 182, 73) when the correspondence indicated by thepixel value table 5 e has been determined using the correspondencebetween color element levels and luminance levels shown in FIG. 11.Therefore, in the pixel value table 5 e of FIG. 6, the arrangementpattern “x10 000 01x x” of the sub-pixels corresponding to a basicportion previously corresponds to the pixel values (182, 182, 73) of thepixel. The other arrangement patterns previously correspond to the pixelvalues of pixels.

FIG. 7 is a diagram showing another example of the pixel value table 5e. FIG. 7 shows a correspondence between the arrangement of sub-pixelscorresponding to a basic portion and the pixel values (R, G, B) ofpixels, where the color of a background is orange, i.e., (R, G, B)=(255,127, 0). The left-hand side of FIG. 7 shows an arrangement pattern of 9sub-pixels contained in 3 pixels which are arranged in the samedirection as that of the arrangement of the sub-pixels. The right-handside of FIG. 7 shows the luminance value of each sub-pixel (R, G, B)contained in a pixel of interest, corresponding to each arrangementpattern in the middle of FIG. 7.

The pixel value of a pixel is determined using the pixel value table 5 eindicating a correspondence between the arrangement of sub-pixelscorresponding to the basic portion of a character and the luminancevalues of sub-pixels contained in a pixel whose pixel value to bedetermined.

For example, it is assumed that the arrangement of sub-pixelscorresponding to a basic portion is “000 000 000”. In this case, thereis no sub-pixel corresponding to the basic portion of a character. Apixel whose pixel value is to be determined corresponds to a background.Therefore, the luminance value of (R, G, B) is (255, 127, 0).

The color element levels of sub-pixels neighboring a basic portion,which are stepwise changed, are adjusted according to the distributionof luminance in the background color. For example, it is assumed thatthe arrangement of sub-pixels corresponding to the basic portion is “000001 000”. When the background color is white, the arrangement of colorelement levels is “001, 257, 521” as shown in FIG. 4. The color elementlevels (2, 5, 7) of sub-pixels (R, G, B) contained in a pixel ofinterest whose pixel value is to be determined are converted toluminance levels (182, 73, 0). In contrast, when the background color isorange, the ratio of the luminance levels (R, G, B) is (1, 1/2, 0).Therefore, the color element levels (2, 5, 7) of the sub-pixels (R, G,B) contained in the pixel of interest whose pixel value is to bedetermined are converted to luminance levels (182, 36, 0) where thelevel of G is adjusted to 73×1/2≅36. Thus, in the pixel value table 5 eof FIG. 7, the arrangement pattern “000 001 000” of the sub-pixelscorresponding to the basic portion previously corresponds to theadjusted pixel values (182, 36, 0) of the pixel. The other arrangementpatterns previously correspond to the pixel values of pixels.

A correspondence between the arrangement of sub-pixels and the pixelvalue of a pixel to be set for any character color and background color,can be adjusted according to the character color and background colorbased on the pixel value table 5 e indicating a correspondence for abasic color combination, i.e., black characters in a white background asshown in FIGS. 3 and 4. For each color combination, the pixel value of apixel can be determined according to a pixel value table 5 e as shown inFIG. 7.

For each combination of a character cooler and a background color, apixel value table as shown in FIG. 7 may be prepared, or the values of apixel value table as shown in FIGS. 3 and 4 may be adjusted so as todetermine a correspondence between the arrangement of sub-pixels and apixel value. When there are a number of combinations of a charactercolor and a background color, similar colors may be grouped and pixelvalue tables indicating a correspondence are prepared for respectiverepresentative colors. In this case, pixel value tables indicating acorrespondence may be adjusted according to the size of a differencebetween the character and background colors and the representativecolor. For example, the sum of squares of differences between each color(R, G, B), the sum of absolute differences between each color (R, G, B),or the like, can be used as an indicator for determining the size of acolor difference. A difference in color element level in color space(e.g., YUV space, Lab space, or the like) based on visualcharacteristics may be used as an indicator for determining a colordifference. If a difference between a representative color assigned tothe above-described pixel value table indicating a correspondence and acolor specified in displaying a character is less than or equal to apredetermined threshold, the specified color is determined as a colorbelonging to a group including the representative color and the pixelvalue table can be used to determine the pixel value of a pixel.

The above-described pixel value table 5 e indicating a correspondencebetween the arrangement of sub-pixels and the pixel value of a pixel has2^((M+2×N)) entries of arrangement combinations of sub-pixels, i.e., thecombinations of the presence or absence (“1” or “0”) of a basic portionin (M+2×N) sub-pixels. For example, if M=N=3, the number of entries is512. As shown in FIG. 10, however, correction patterns arepredetermined, in which the color element levels of sub-pixelsneighboring a sub-pixel corresponding to a basic portion are stepwisechanged. Therefore, the sequence of the luminance values of sub-pixelsis limited. When correction patterns overlap in a sub-pixel, the largercolor element level is set in the sub-pixel. Therefore, the number ofpixel values obtained by combinations of sub-pixels is 5×N+8 where M=3.Therefore, if M=N=3, the number of pixel values is 23. By assigning 23indexes to 512 arrangement patterns, a data capacity for storing pixelvalues actually prepared can be reduced as compared to when 24-bit fullcolor data is prepared in a table where each of (R, G, B) has a lengthof 8 bit (=0 to 255). Note that the number of combinations is notlimited to 23 when pixel values are set more precisely.

As described above, a table indicating a correspondence between thearrangement pattern and luminance levels of sub-pixels in a directionalong which R, G, and B are arranged, is used to determine the luminancelevels of sub-pixels contained in a pixel of interest. The presentinvention is not so limited. Alternatively, the luminance level ofsub-pixels in a pixel of interest may be determined based on anarrangement pattern of sub-pixels in a direction perpendicular (oroblique) to the direction along which R, G, and B are arranged, forexample. In this case, a table indicating a correspondence between thearrangement pattern and luminance levels of sub-pixels arranged in theperpendicular (or oblique) direction, is used.

FIG. 8 is a flowchart indicating a process flow of the display program41 b (FIG. 1) when the character shape data 5 b is skeleton data.

In step S101, a character code and a character size are input throughthe input device 7. For example, when a Kanji character “

” is displayed on the display device 3, 4458 (JIS KUTEN code, 44thsection and 58th point) is input as a character code. The character sizeis represented by the number of dots in a horizontal direction and thenumber of dots in a vertical direction, e.g., 20 dots×20 dots, forexample.

In step S102, skeleton data corresponding to the input character code isread from the character shape data 5 b in the auxiliary memory apparatus40 and is then stored in the main memory 4 of the control apparatus 20.This skeleton data contains a character code for identifying the type ofa character, the number of strokes constituting a single character, thenumber of points constituting a single stroke, the line type of astroke, the coordinates of points constituting a single stroke, and thelike.

In step S103, the coordinate data of points constituting each stroke isscaled according to the character size input through the input device 7.This scaling converts the coordinate data in the skeleton data definedin a predetermined coordinate system to a real pixel coordinate systemfor the display device 10. In this case, the scaling is performed byconsidering the arrangement of sub-pixels. As shown in FIG. 2A, forexample, one pixel 10 comprises three sub-pixels 11 arranged in an Xdirection. When a character size is 20 dots×20 dots, the coordinate dataof the skeleton data is scaled into data of 60(=20×3) pixels×20 pixels.

In step S104, the coordinate data of points constituting a stroke isobtained. In step S105, it is determined whether the type of the strokeis a straight line or a curved line from the line type of the strokecontained in the skeleton data. When the type of the stroke is astraight line, the process goes to step S106. When the type of thestroke is a curved line, but not a straight line, the process goes tostep S107.

In step S106, the points constituting the stroke are linked withstraight lines, and sub-pixels on the straight lines are defined as thebasic portion representing the skeleton of a character. In step S107,the coordinate data of the points constituting the stroke isapproximated by curved lines, and sub-pixels positioned on the curvedlines are defined as the basic portion representing the skeleton of acharacter.

In step S108, it is determined whether or not all strokes contained in acharacter have been processed. If “Yes”, the process goes to step S109.If “No”, the process returns to step S103 and is continued.

In step S109, the arrangement pattern of the sub-pixels in a pixel ofinterest whose pixel value (the luminance levels of sub-pixels) is to bedetermined and its neighboring pixels, is determined.

In step S110, a pixel value of the pixel of interest corresponding tothe arrangement pattern of the sub-pixels determined in step S109 isdetermined as the luminance levels of sub-pixels contained in the pixelof interest according to the pixel value table 5 e indicating acorrespondence between the arrangement pattern of sub-pixelscorresponding to a basic portion and the pixel value (the luminancelevels of sub-pixels) of a pixel.

In step S111, luminance data indicating the luminance levels of thesub-pixels set in step S110 is transferred to the display device 3.

As described above, the luminance level can be adjusted on asub-pixel-by-sub-pixel basis based on the arrangement of sub-pixelscorresponding to a basic portion for the purpose of displaying acharacter on the display device 3. In the above-described embodiment,sub-pixels corresponding to the basic portion indicating the skeleton ofa character are obtained from skeleton data. Alternatively, suchsub-pixels may be obtained from outline data, bitmap data, or the likeby a predetermined process. Alternatively, the pattern of the basicportion may be previously stored as character shape data in theauxiliary memory apparatus 40 and may be read as required.

INDUSTRIAL APPLICABILITY

As described above, according to the present invention, when a characteris displayed with a high resolution on a display section capable ofdisplaying color, a luminance level to be displayed on the displaysection can be obtained directly by converting the arrangement patternof sub-pixels corresponding to the basic portion representing theskeleton of a character. Therefore, the character display process can beperformed at a higher rate and a working memory area for performing thecharacter display process can be reduced. As a result, character displayprocessing can be performed at a higher rate and the hardware cost canbe reduced.

According to the present invention, when character strokes are close toeach other, the positions of sub-pixels corresponding to the basicportion representing the skeleton of a character can be adjusted toeasily prevent deformation of a character. Further, in addition to asub-pixel corresponding to the basic portion representing the skeletonof a character, its neighboring sub-pixels are allowed to represent thebasic portion, thereby making it possible to easily increase the linewidth of the character.

Any color may be assigned to a character to be displayed and abackground. In this case, by changing a correspondence between thearrangement of sub-pixels and the luminance levels of sub-pixelsaccording to the character color and the background color, it ispossible to provide a character display in which the shape of acharacter is retained and a high level of visibility is achievedirrespective of a color combination.

Similar combinations of a character color and a background color may begrouped. In this case, correspondences between the arrangement patternof sub-pixels corresponding to a basic portion and the pixel value of apixel for a group of color combinations can be merged into acorrespondence for a representative color combination. Therefore, a dataamount required for a correspondence table between the arrangementpattern of sub-pixels corresponding to a basic portion and the pixelvalue of a pixel can be reduced.

Various other modifications will be apparent to and can be readily madeby those skilled in the art without departing from the scope and spiritof this invention. Accordingly, it is not intended that the scope of theclaims appended hereto be limited to the description as set forthherein, but rather that the claims be broadly construed.

1. A character display apparatus, comprising: a display devicecomprising a plurality of pixels; and a control section for controllingthe display device, wherein each of the plurality of pixels comprises aplurality of sub-pixels arranged in a predetermined direction, and atleast one of a plurality of color elements is assigned to each of theplurality of sub-pixel; the control section determines at least onesub-pixel, to which a basic portion indicating a skeleton of a characteris assigned, among the plurality of sub-pixels in the display device,based on character shape data indicating character shapes; a first pixelof the plurality of pixels comprises a plurality of first sub-pixels; atleast one pixel neighboring the first pixel comprises a plurality ofsecond sub-pixels; the control section determines an arrangement patterncontaining a plurality of elements, wherein a value of each of theplurality of elements is determined depending on whether or not thebasic portion is assigned to a corresponding sub-pixel of the pluralityof the first sub-pixels and the plurality of the second sub-pixels; andthe control section introduces a predetermined change into thearrangement pattern, the predetermined change including one ofreplacement of a position of the basic portions and duplication of thebasic portion, and determines a luminance level of only the first pixelbased on the changed arrangement pattern, wherein the luminance level ofthe first pixel based on the changed arrangement pattern is determinedusing a stored table indicating a predetermined correspondence betweenarrangement patterns of sub-pixels and luminance levels of sub-pixelsarranged in a certain direction, which is one of the same as thepredetermined direction and different from the predetermined direction,and the correspondence indicated by the stored table is determined usinga predetermined correction pattern of color element levels of sub-pixelsneighboring a sub-pixel corresponding to the basic portion.
 2. Anapparatus according to claim 1, wherein the plurality of elementsinclude a first element and a second element neighboring the firstelement; a value of the first element indicates that the basic portionis assigned to a sub-pixel relating to the first element; a value of thesecond element indicates that the basic portion is not assigned to asub-pixel relating to the second element; and the control sectiondetermines the luminance level of the first pixel based on anotherarrangement pattern which is modified from said arrangement pattern suchthat a value of the first element is interchanged with a value of thesecond element.
 3. An apparatus according to claim 1, wherein theplurality of elements include a first element and a second elementneighboring the first element; a value of the first element indicatesthat the basic portion is assigned to a sub-pixel relating to the firstelement; a value of the second element indicates that the basic portionis not assigned to a sub-pixel relating to the second element; and thecontrol section determines the luminance level of the first pixel basedon another arrangement pattern which is modified from said arrangementpattern such that a value of the second element is changed to indicatethat the basic portion is assigned to the sub-pixel relating to thesecond element.
 4. An apparatus according to claim 1, wherein thecontrol section determines the luminance level of the first pixel basedon a combination of a color of the character and a background color ofthe character and the arrangement pattern.
 5. An apparatus according toclaim 1, wherein the control section compares a combination of a colorof the character and a background color of the character with acombination of a predetermined character color and a predeterminedbackground color, and determines the luminance level of the first pixelbased on a result of the comparison and the arrangement pattern.
 6. Amethod for displaying a character on a character display apparatus,wherein the character display apparatus comprises: a display devicecomprising a plurality of pixels; and a control section for controllingthe display device, wherein each of the plurality of pixels comprises aplurality of sub-pixels arranged in a predetermined direction, and atleast one of a plurality of color elements is assigned to each of theplurality of sub-pixel; a first pixel of the plurality of pixelscomprises a plurality of first sub-pixels; and at least one pixelneighboring the first pixel comprises a plurality of second sub-pixels,the method comprises the steps of: determining at least one sub-pixel,to which a basic portion indicating a skeleton of a character isassigned, among the plurality of sub-pixels in the display device, basedon character shape data indicating character shapes; determining anarrangement pattern containing a plurality of elements, wherein a valueof each of the plurality of elements is determined depending on whetheror not the basic portion is assigned to a corresponding sub-pixel of theplurality of the first sub-pixels and the plurality of the secondsub-pixels; and introducing a predetermined change into the arrangementpattern, the predetermined change including one of replacement of aposition of the basic portions and duplication of the basic portion, anddetermining a luminance level of only the first pixel based on thechanged arrangement pattern, wherein the luminance level of the firstpixel based on the changed arrangement pattern is determined using astored table indicating a predetermined correspondence betweenarrangement patterns of sub-pixels and luminance levels of sub-pixelsarranged in a certain direction, which is one of the same as thepredetermined direction and different from the predetermined direction,and the correspondence indicated by the stored table is determined usinga predetermined correction pattern of color element levels of sub-pixelsneighboring a sub-pixel corresponding to the basic portion.
 7. Arecording medium storing a program for causing a character displayapparatus to execute a character display process, wherein the recordingmedium is readable by the character display apparatus, the characterdisplay apparatus comprises: a display device comprising a plurality ofpixels; and a control section for controlling the display device,wherein each of The plurality of pixels comprises a plurality ofsub-pixels arranged in a predetermined direction, and at least one of aplurality of color elements is assigned to each of the plurality ofsub-pixel; a first pixel of the plurality of pixels comprises aplurality of first sub-pixels; and at least one pixel neighboring thefirst pixel comprises a plurality of second sub-pixels, and Thecharacter display process comprises the steps of: determining at leastone sub-pixel, to which a basic portion indicating a skeleton of acharacter is assigned, among the plurality of sub-pixels in the displaydevice, based on character shape data indicating character shapes;determining an arrangement pattern containing a plurality of elements,wherein a value of each of the plurality of elements is determineddepending on whether or not the basic portion is assigned to acorresponding sub-pixel of the plurality of the first sub-pixels and theplurality of the second sub-pixels; and introducing a predeterminedchange into the arrangement pattern, the predetermined change includingone of replacement of a position of the basic portion and duplication ofthe basic portion, and determining a luminance level of only the firstpixel based on the changed arrangement pattern, wherein the luminancelevel of the first pixel based on the changed arrangement pattern isdetermined using a stored table indicating a predeterminedcorrespondence between arrangement patterns of sub-pixels and luminancelevels of sub-pixels arranged in a certain direction, which is one ofthe same as the predetermined direction and different from thepredetermined direction, and the correspondence indicated by the storedtable is determined using a predetermined correction pattern of colorelement levels of sub-pixels neighboring a sub-pixel corresponding tothe basic portion.